The invention is based on an optical fibre amplifier comprising at least one pump light source (3), at least one amplifying fibre section (10), and at least one coupler (8) which establishes a connection between the input fibre (1) of the fibre type I, the pump light source (3), the amplifying fibre section (10) and the output fibre (12) of the fibre type I.
Different fibre amplifiers employing many different types of amplifying fibres are known from the prior art. For example, U.S. Pat. No. 5,973,824 is known, which describes the production and use of an amplifying fibre composed of a glass composition of germanium, arsenic, selenium and sulphur. It is also known to use other non-oxidic types of glass as material for amplifying fibres. In particular, the use of materials consisting of halides and sulphides doped with rare earths as amplifying fibres seems promising. Compared to silica glass, halide- and in particular fluoride glass has transparent properties which extend spectrally substantially further into the long-wave range. This is due to the spectral shift of the multi-phonon absorption edge as a result of the incorporation of substantially heavier ions. However, these types of glass present technological difficulties in respect of material production and fibre preparation. Their unfavourable mechanical properties and unfavourable behaviour in humid atmospheres have so far prevented their large-scale use. Recently it has been possible to produce fibre amplifiers operating with fibres composed of ZBLAN (Zrxe2x80x94Baxe2x80x94Laxe2x80x94AILxe2x80x94Na) fluoride glass. Due to its relatively high refractive index and the flexibility of its composition, sulphide glass can be considered as a promising candidate for use as amplifying material. Therefore great efforts are being undertaken world-wide to produce many different types of halide glass with low phonon energies. As disclosed in U.S. Pat. No. 5,973,824, the special fibres, which in the following description will be referred to as xe2x80x9cfibre type IIxe2x80x9d, are glued-in by means of glue splices between the standard, silica-based glass fibres, referred to in the following as xe2x80x9cfibre type Ixe2x80x9d. Because of the different thermal coefficients of silica fibres (fibre type I) and halide fibres (fibre type II), the fused splices normally employed in telecommunications technology cannot be used. It is therefore only possible to use mechanical splices or glue splices. As mechanical splices have disadvantages in terms of the precision and permanence of their positioning, the fibres of fibre type I and fibre type II are joined using glue splices. The refractive index adaptation and mechanical stabilization of a glue splice are achieved by the use of a special glue. The behaviour of this index-adaptable special glue is critical with regard to aging and premature embrittlement due to loading with UV-light.
The optical fibre amplifier according to the invention comprising at least one pump light source 3, at least one amplifying fibre section 10, and at least one coupler 8 which establishes a connection between the input fibre of the fibre type I, the pump light source 3, the amplifying fibre section 10 and the output fibre 12 of the fibre type I, has the advantage that all the splice connections between the fibre type I and the fibre type II are located at a distance from the amplifying fibre section such that short wavelength light is already noticeably attenuated. The optical fibre amplifier is constructed such that the critical glue splices are exposed to a reduced proportion of UV light as the critical short-wave light of the blue- and UV-wavelength is attenuated by a suitable absorbent means.
Advantageous further developments and improvements of the optical fibre amplifier described in the main claim are possible as a result of the measures described in the sub-claims.